Apparatus for applying adhesive to wood stock



A. H. DE MEERLEER I 3,508,523

A ril 28, 1970 APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK 5Sheets-Sheet 1 INVENTOR.

Albert H. DeMeer/eer April 28, 1970 A. H. DE MEERLEER 3,508,523

APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK 5 Sheets-Sheet 2 Filed May15, 1967 1' N VEN TOR.

A/berf H. DeMeer/fi'r BY MK ATTORNEY April 1970 A. H. DE MEERLEER3,508,523

APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK Filed May 15, 1967 5Sheets-Sheet 3 INVENTOR. A/berf H. De Meek/ear ATTORNEY April 1970 A. H.DE MEERLEER 3,508,523

APPARATUS FOR APPLYING ADHESIVE TO WOOD STOCK Filed May 15, 1967 5Sheets-Sheet 4 INVENTOR' A/berf H. Dee/486F168? April 28, 1970 A. H. DEMEERLEER 3,508,523

APPARATUS FOR APPLYING ADHESIVE TO woon STOCK Filed May 1.5, 196? 5SheetsSheet 5 INVENTOR. A/berf H. De Meek/66;

ATTORNEY United States Patent 3,508,523 APPARATUS FOR APPLYING ADHESIVETO WOOD STOCK Albert H. De Meerleer, Tacoma, Wash., assignor to PlywoodResearch Foundation, Tacoma, Wash., a

corporation of Washington Filed May 15, 1967, Ser. No. 638,461 Int. Cl.B44d 1/48 U.S. Cl. 118-63 4 Claims ABSTRACT OF THE DISCLOSURE Thisinvention relates to a process and apparatus for applying an adhesivelayer of substantially uniform thickness to a wood stock surface, asplywood veneer, regardless of thickness variations of the wood stock andsurface deviations from a planar surface. In general, the inventioncontemplates the applying of an adhesive to the surface of the wood toprovide a substantially uniform composite thickness of wood stock andadhesive and then the removing of excess applied adhesive over apredetermined substantially uniform adhesive thickness and thisregardless of the wood stock thickness and the deviations of a woodstock surface from a planar surface. The excess applied adhesive isremoved by means of an air knife comprising a tubular member with aplurality of spaced openings. The tubular member is kept clean by meansof a reciprocating scraper mounted thereon.

The prior art of laying up plywood, or providing a sandwich comprising awood core with a wood veneer front or back face (or both) on the woodcore, contemplated the use of an adhesive between contacting woodsurfaces and the adhesive used was generally in a liquid form. The saidwood cores comprise: a wood veneer sheet, plywood formed of Wood veneersheets, chipboard, hardboard, flakeboard, and lumber stock. Theconventional means in the prior art for applying such liquid adhesiveprovided travel to wood core by feeding it between rotatably driven gluespreader rolls, either metallic or rubber coated metallic rolls, andattempted to apply a uniform coat of liquid adhesive to the gluespreader rolls by the use of doctor rolls. However, the prior art failedto provide a uniform coating of the adhesive on the wood surfaceregardless of how uniform the adhesive was spread on the rolls.

One of the reasons for such failure to provide for uniform spread ofadhesive on the wood surfaces resides in the fact that the wood core isnot uniform in thickness and rotatably driven glue rolls, even whenoperating under optimum conditions, only attempt to determine a uniformcomposite thickness of wood core and adhesive, and thus any variationsin thickness of the wood core result in a complementary variation in thethickness of the adhesive applied to the wood core. Thus, the thicknessof the adhesive layer increases at the areas of lesser thickness of woodcore and decreases at the areas of greater thickness of wood core.

Another reason for such failure to provide even spread of adhesive onthe wood stock lies in the fact that the surfaces of the wood stock towhich the adhesive is applied are nonplanar and have deviationstherefrom generally characterized by ridges and valleys.

Another reason for such failure to provide a uniform spread of liquidadhesive is that the glue spreader rolls are subject to excessive wearby the frictional contact which the rolls (acting by frictional contactto function as a conveyor for the wood stock) have with the rough woodsurfaces on which they are applying adhesive. Generally, workmennormally feed more wood stock in certain laterally disposed areas thanothers and thus there is not only generally surface wear of the gluespreader rolls but there are areas of greater wear disposed laterally onthe glue spreader rolls. This wear adversely affects the uniformity ofglue spread of said glue rolls even to provide a uniformity of compositethickness of wood stock and adhesive.

In the hot pressing of plywood, wood veneer sandwiches are commerciallyloaded into the openings of multiple opening hot presses. A large numberof panels are pressed at one time, such as between 20 and 40. Eachsandwich is given the same treatment as to temperature, pressure, andtime, and thus each uncured sandwich must be as near as possible to theothers to obtain uniformity in the finished plywood panel.

Due to the fact that the installed cost of plywood hot presses in aninvestment in the order of some hundreds of thousands of dollars, themaximum production possible is a necessity. Such maximum productionrequires that the sandwiches must conform to the requirements of the hotpresses rather than having the hot presses conform to the variousrequirements of individual sandwiches. Thus, a predetermined pressingcycle and conditions are determined, such as: pressurep.s.i.; platentemperatures-285 F. to 300 F.; press close or pressing timea definitetime selected, generally in the range of 3 /2 to 6 minutes; and a pressopening selected time, depending upon the time requirements of automaticloaders and unloaders employed and in the order of 1 minute.

In order to make the requirements of the individual sandwiches asuniform as possible, very substantial improvements have been made in theart to improve the adhesives employed, the veneer dryers employed, andmoisture meters to ensure that the veneer moisture content of thevarious veneer employed is within a given range. However, the feature ofproviding a uniform thickness layer of adhesive on the wood veneersurfaces to be adhered together has heretofore eluded the practicalcommercial arts.

With prior art conventional glue spreader rolls, the optimum possibleresult will be a uniform composite thickness of adhesive and wood stock.Thus, in general, there is excess adhesive at thin areas of the Woodstock and too little adhesive at the thick areas thereof. However, thewood stock must contact the adhesive on the glue rolls to remove gluetherefrom and deposit the same on the wood stock. Thus, if the woodstock is too thin to make such contact (even though the wood stock isusable) no adhesive will be deposited on the wood stock at such areas.When workmen see areas of wood stock on which there has been no depositof adhesives, they promptly discard such wood stock and the same isthrown away. The loss involved is not only the loss of wood stock but isthe loss of the adhesive on portions of the said thrownaway wood stock.It is a primary object of this invention to minimize the loss of suchmaterials.

On extra thick areas of wood stock and where the glue spread is too thinor a starved glue line exists, a condition exists which is diflicult tobe determined by eyesight and hence the error generally is notdiscovered until after the sandwiches have been pressed and cured andthen the loss is in plywood panels. Such loss in plywood panels isobviously a greater loss and the amount of the loss increases as thetime required for discovery increases. Obviously, if the same is notdiscovered until the panels are used in connection with structures, thenthe potential loss will include the structures as well as the panels.

In areas where the adhesive thickness is excessive, there are oftenpools of adhesive and such pools cannot readily be seen by the workmen.Thus, they generally continue to exist until the sandwiches are pressedand the adhesive cured. With areas or pools of excessive glue, there isthe adverse result of uncured glue and improper bonding, because thewood surfaces to be adhered together are spaced apart and do not haveproper contact. It must be remembered that liquid adhesives arenoncompressible and will thus provide means to maintain wood surfacesspaced. While at times the pressure utilized in the presses will causemigration of the glue tending to break down pools of excessive glue, yetat many times the glue cannot migrate laterally and the pools remain andthe problems incident in blows and blisters are still a major problem inthe plywood art. While the blows and blisters are common in the hotpressing of plywood, yet excessive glue areas still provide improperbonding in cold pressing of plywood panels. In any event, excessive glueareas and starved glue lines are to be avoided whether the panels arehot pressed or cold pressed. The prior art failed to provide uniformspread of adhesive on wood surfaces and this primarily because of thenaturally occurring differences in thickness of the wood stock and thenaturally occurring surface defects and variations of the wood surfacefrom a planar surface. It is a primary object of this invention toprovide a uniform spread of adhesive on wood surfaces in the plywoodart.

As wood stock passes through the conventional glue spreader rolls, theareas where no adhesive has been shpread are often visible. Thus, thepractice in the art has been to increase the thickness of adhesivespread by the conventional glue spreader rolls to limit the amount ofreadily seen areas on which there is no adhesive. This practice has notonly increased the problems resulting from overspread as blows,blisters, and improper bonded areas but has resulted in the usage ofexcess amounts of glue, all resulting in a very substantial loss toindustry. Thus, this invention, in providing a process and apparatus forproviding a substantially uniform spread of adhesive on wood stocksurfaces, has a primary object in the saving of the total amount ofadhesive used.

Another object of this invention is the providing of a uniform coatingof adhesive on a surface of rotary cut wood veneer.

Another object of this invention includes the spreading of excessadhesive on a surface of a piece of wood stock and then the removal ofall excess adhesive over a predetermined uniform thickness of adhesiveregardless of the thickness of the piece of wood stock or the surfacecontour thereof.

Another object of this invention is to remove such excess of adhesive byuse of a tubular member, air supply means for said tubular member, andspaced apart longitudinally alined openings in said tubular member, andspaced apart longitudinally alined openings in said tubular memberproviding jets of air impinging upon said excess adhesive and moving thesame away from the jets of air.

Another object of this invention is to direct such jets of air so thesame impinge upon the adhesive coating on said surface and at acuteangles thereto.

Another object of this invention is to maintain a relatively horizontalposition of the adhesively coated wood surface at the time of impingingsaid jets of air thereagainst.

Another object of this invention is to maintain said tubular membersfree and clear of foreign matter, such as adhesive or adhesivecontaining residues.

Other objects of this invention will now become apparent from thedetailed description of the invention and the following description ofthe drawings, throughout which like reference numerals relate to likeparts.

FIGURE 1 is a fragmentary and somewhat schematic view of a deviceembodying this invention and with the veneer guides only generally andfragmentarily shown in view of the scale to which FIG. 1 is drawn;

FIG. 2 is a front elevational view of the device of FIG. 1 applied to aconventional glue spreader used in the plywood art and with parts brokenaway;

FIG. 3 is a somewhat schematic view, on a much smaller scale than FIGS.1 and 2, and showing primarily mounting means for this invention;

FIG. 4 is a view, partly in section and partly in elevation, takensubstantially on broken line 44 of FIG. 2 and on a larger scale than theshowing in FIG. 2;

FIG. 5 is a fragmentary sectional view, with parts shown in elevation,and on a larger scale than FIG. 4 and taken substantially on broken line55 of FIG. 2;

FIG. 6 is a fragmentary view of structure shown in FIG. 5 on a largerscale than FIG. 5;

FIG. 7 is a fragmentary perspective view of parts of the structure shownin FIG. 1 of the drawings particularly indicating, more completely, theveneer guides shown only fragmentarily in FIG. 1 of the drawings;

FIG. 8 is a fragmentary view showing an alternate form of veneer guidesand particularly applicable for use in connection with veneer fed in adirection at right angles to the wood grain thereof;

FIG. 9 is an end elevational view of the structure of FIG. 8;

FIG. 10 is an enlarged fragmentary view, taken substantially on brokenline 10'10 of FIG. 6, and illustrates one type of air knife cleanermeans which may be employed with this invention;

FIG. 11 is a fragmentary sectional view on a larger scale, takensubstantially on broken line 1111 of FIG. 10 and also illustrating asheet of material to which adhesive has been applied;

FIG. 12 is an enlarged fragmentary view of the showing of FIG. 11 as toair knife adhesive spreader;

FIG. 13 is a fragmentary enlarged sectional view of parts shown in FIG.10 of the drawings;

FIG. 14 is a fragmentary perspective view of parts shown in FIG. 6 ofthe drawings;

FIG. 15 is a fragmentary view of one form of air knife cleaner meanswhich may be used with this invention;

FIG. 16 is an enlarged fragmentary view showing additional details ofthe air knife cleaning system depicted in FIG. 15 of the drawings; and

FIG. 17 is a fragmentary and somewhat schematic view of an alternateform of cleaning means for the air knife.

Referring more particularly to FIG. 1 of the drawings, the device ofthis invention may be connected with and operate in conjunction with theglue spreader rolls of a conventional glue spreader commonly used inconnection with the manufacture of plywood. Such a conventional gluespreader will comprise an upper adhesive applicator roll 20, an upperadhesive doctor roll 22, and end plates 24 so that an adhesive well isformed between the rolls 20 and 22 and the end plates 24. This adhesivewell contains adhesive of suitable characteristics and to a desiredlevel. The rolls turn in the direction of the arrows and thus the doctorroll 22, which is adjustable toward and away from the adhesiveapplicator roll 20 (by conventional meansnot shown), will determine anadjusted layer thickness of adhesive present on adhesive applicator roll20 at the time a piece of veneer 26 is passing under and contacts theadhesive applicator roll 20.

The lower surface of the veneer 26 is contacted by the lower adhesiveapplicator roll 28 as the veneer 26 passes over the same. The layerthickness of adhesive present on the said roll 28 at this time isdetermined by a lower doctor roll 30 which is adjustable toward and awayfrom the lower adhesive roll 28 (by conventional meansnot shown). In theform of conventional adhesive spreader shown in FIG. 1 where the doctorroll 30 precedes the lower adhesive roll 28 in the direction of travelof the veneer 26, an adhesive trough 32 is employed and the loweradhesive applicator roll 28 extends into the trough 32 and below thesurface level of adhesive in said glue trough 32. Other types of lowerglue applicator-doctor roll combinations are commonly employed and thusthe type illustrated is to be considered illustrative and notrestrictive.

It is common to adjust doctor rolls 22 and in the plywood art to spreadglue at predetermined rates, such as a rate of about 60 pounds of wetglue per thousand square feet of double glue line for exterior typeglue.

This invention contemplates the employment of the adhesive spreader airknives, and associated parts exemplified in FIG. 1 by upper tubularmember 34 and lower tubular member 36. These tubular members 34 and 36cause air to be directed out through openings therein, all of which isconsidered and explained in detail in connection with later figures.However, these said tubular members 34 and 36 require periodic cleaningof the exterior surface thereof to remove residue, including adhesive,and as an illustration of cleaner-scraper means, there is indicated inconnection with FIG. 1 of the drawings the scrapers 38 and 40 which aremounted for traveling movement respectively on said tubular members 34and 36 and for travel from one side of the machine to the other and fromsaid other side of the machine back to the first mentioned side. Thesaid tubular members 34 and 36 are connected with the devices of thisinvention by means later described.

One way of causing said travel of the tubular scraper and cleanermembers 38 and 40 is to connect the same with an endless cable means 42.Endless cable means 42 is reeved about suitable main pulleys 44, 46, 48,and and alinement of said endless cable means 42 is obtained by saidpulleys and also by guide pulleys 52, 54, and 56. As it is desired tomake devices of this invention either as a part of a combinationadhesive spreader or as accessories usable in connection with existingadhesive spreader rolls, preferably the pulleys mentioned are employedso that there will be a flight of the cable 42 in a suitable direction,shown as vertical, so as to minimize space requirements or to ensurethat there will be sufficient room to attach the device as an accessoryto existing glue Spreaders. Also, in view of the fact that the verticalflight, as shown in FIG. 1, must have suitable length, a break line isshown to indicate any desired length of the vertical flight.

One means of causing said endless cable means 42 to travel crosswise ofthe machine and sequentially in either direction is to connect the sameby connector 64 to a driven endless cable 62. Endless cable 62 is reevedabout driven sprocket 58 and idler sprocket 60 and thus is driven.Driven sprocket 58 is connected to any suitable source of rotary power(not shown) and is selectively driven a desired amount in eitherdirection (by means not shown) to determine the direction and amount ofturning movement of driven sprocket 58, and in turn the amount anddirection of travel of endless cable means 62 and endless cable means42.

FIGS. 1 and 2 show mounting means for the tubular members 34 and 36 andassociated parts. Some of the parts are broken away in FIG. 2 of thedrawings in view of the scale to which said figure is drawn. FIG. 3 isdrawn to a smaller scale and shows somewhat more completely the mountingmeans. The adhesive applicator rolls 20 and 28 are shown in FIG. 3 (on alarger scale in FIG. 2) and are carried by suitable bearings. Two ofsuch bearings 63 and 65 are shown to the right in FIG. 2 of thedrawings. Such bearings are supported by the main frame of aconventional adhesive spreader used in the plywood art and to which thedevice of this invention may be applied either as an accessory or thesame may be fabricated together as a combination. The tubular members 34and 36, and associated parts operating in conjunction therewith (many ofwhich have been previously described), are mounted separately of themain machine frame of the conventional adhesive spreader so that all ofsaid associated parts are movable into operative position relative tothe applicator rolls 20 and 28 or they are movable out of operativeposition relative thereto to permit usual maintenance and repair of theconventional glue spreader and movement of the tubular members 34 and 36and associated parts as a safety precaution in case of a jarnb of veneeror other possible faulty operation.

The support for such tubular members 34 and 36 and associated parts maycomprise a vertical standard 68 (see FIG. 3) rotatably mounted on afixed base 70. The base 70 and main machine frame (not shown) may be suported at a common floor level.

The upper frame 74 for directly supporting the upper tubular member 34and associated parts and indirectly supporting lower tubular member 36and associated parts (as will be later explained) is secured at one erdportion thereof to vertical standard 68 by hearing 76. The other endportion of the upper frame 74 is suspendedly supported by rigid means 78(shown in FIG. 3 and with a fragment thereof shown in FIG. 2). The rigidmeans 78 is connected at one end portion thereof to the upper frame 74and at the other end portion thereof to standard 68 by connecting means80 (see FIG. 3). The tubular members 34 and 36 are supported at theirend portions by cross frames or strong backs 79. The tubular scrapermembers 38 and 40 are supported on groove tracks (see also FIG. 14)carried by the cross frames 79, as will be more specifically laterdescribed. Also, cross frames 79 support upper veneer guides 82 andlower veneer guides 84 as a strong back therefor. Thus, all of the saidparts will swing together as a unit with rotation of vertical standard68.

The said upper frame 74 is releasably connected with a main framestructure part 81 (see FIG. 2-upper right) by releasable means 83carried by upper frame 74. At all times during normal operation, theswinging structure of this invention will be relatively fixed to themain frame of the machine supporting the adhesive applicator rolls 20and 28 and parts associated therewith.

The adhesive applicator rolls 20 and 28 wear with use and thus losetheir precise cylindrical configuration and it becomes necessary toplace them on a lathe, from time to time, and to turn them down to adiameter so they are true cylinders. As a practical expedient inconventional adhesive Spreaders, the operative axis of only one of saidapplicator rolls 20, 28 is fixed and the axis of the other thereof (aslower adhesive applicator roll 28) is adjustable toward and away fromthe fixed axis of the other (upper adhesive applicator roll 20).

Also, to adjust for different thicknesses of veneer, the spacing betweenadhesive applicator rails 20 and 28 must be adjusted. As the center linebetween applicator rolls 20 and 28 changes in elevation and they changein diameter, the center line between the tubular members 34 and 36 andbetween veneer guides 82 and 84 and their spaced distance to saidadhesive applicator rolls 20, 28 must be adjusted to match such changesin the adhesive applicator rolls 20 and 28. This is accomplished byadjusting the relative position of vertical standard 68 by any suitablemeans (not shown).

Referring generally to FIGS. 4, 5, and 6 of the drawings, only the endportions of the upper tubular member 34 and the end portions of thelower tubular member 36 at both ends of the device are carried by endportions of the upper and lower cross frames 79 (in order to scrapetubular members 34 and 36 throughout their entire lengths they must besupported only at their end portions). The veneer guides 82 and 84 arecarried by the upper and lower cross frames 79 and each guide must besupported for strength requirements. The upper and lower cross frames 79are separately adjustable toward and away from each other to provide adesired extent of opening therebetween, as will be hereinafterexplained.

As the structure of the ends of the machine are identical, FIGS. 4, 5,and 6 illustrate only one end portion of the machine. The lower crossframe or strong back 79 terminates in end portions 100, each of which iscarried by and moves with a slidable end frame 75 (the details thereofwill be explained later). Each end frame 75 is connected with and slideswith a slidable end frame portion 77. End thrust bearings and guides 71and end brackets 88 are supported by the upper frame 74. Vertical shafts90 threadedly engage slidable supports 73. By reason of such threadedengagement between shafts 90 and the slidable supports 73 and the factthat vertical movement of shafts 90 is prevented by end thrust bearing71, turning movement of the shafts 90 imparts vertical travel to thesupports 73 relative to upper frame 74, thrust bearings 71, and endbrackets 88. Such vertical travel of supports 73 is imparted to frames77 and 75 and to the end portions 100 of the lower cross frame 79, aswell as parts connected with said lower cross frame 79. Such associatedparts connected with lower cross frame 79 will include such structure astubular members 36 and lower veneer guides 84.

The vertical shafts 90 (see also FIG. 2) are interconnected by worm andgear means 92, and cross shaft 94. Rotary movement to the cross shaft 94(in either direction) may be imparted by hand wheel 96 connected tocross shaft 94. Thus, upon turning of the hand wheel 96, the lowertubular member 36 and lower veneer guides 84 may be adjusted relative tothe upper tubular member 34 and upper veneer guides 82 to accommodatethe passage of wood stock therebetween, such as veneer, of differentthicknesses. Of course, at the same time, the adhesive applicator rolls20 and 28 are similarly adjusted.

Individual end elevational adjustment of the veneer guides 82 and 84 andparts connected therewith (see particularly FIG. 4) is provided byterminating the upper cross frames 79 in diagonal upper slide guides 98and lower cross frames 79 in lower slide guides 100. The said guides 100are mounted for sliding movement in slots in the slidable end frames 75.Bolts 102 may be employed to interconnect lower slide guides 100 withthe slidable end frames 75 and thus upon loosening and adjustments, therelative position of the slide guides 100 to end frames 75 may bedetermined. This provides for individual vertical adjustments of theends of lower cross frame 79 and parts carried thereby to adjust thelower cross frame 79 into a desired horizontal plane.

Preferably, the slide guides 98 (terminal end portions of upper crossframe 79) are held in place by safety releasable means and with eachhaving adjustable length linkage (not shown) to provide for individualend elevation adjustment of upper slide guides 98 and to thus adjust theupper cross frame 79 into a desired horizontal plane. Such safetyrelease means may comprise pre-loaded safety release air cylinders 104(FIG. 2), which are pre-loaded so that any pressure exerted above saidpre-loading and which pressure may be exerted by veneer jambing betweenveneer guides 82 and '84 (also see FIGS. 5, 6, 7, and 14) will causediagonal guide 98 (FIG. 4) to release and slide in slide guides 98 infixed brackets 88 and thus increase the relative size of the openingbetween veneer guides 82 and 84 and parts carried therewith. Thus, thespacing between veneer guides 82 and 84 may be selected as one suitablefor particular thickness of veneer passing between said veneer guidesbut at the same time in case of a jamb up, there will be a safetyfeature so that the said opening may be increased rapidly andautomatically in response to extra pressure exerted between the veneerguides 82 and 84 caused by malfunction through extra size of veneerpassing therebetween.

The tubular scraper members 38 and 40 are best shown in details in FIGS.5, 6, l0, 11, 13, and 14. As the upper and lower scraper members areidentical, the parts of each thereof are given the same numbers. Thehousing of each scraper comprises two housing parts 106 and 108 (seeFIGS. 6 and 14) held together by set screws 110 and sliding clearancebetween housing 106, 108 and a tubular member 34 or 36 may be obtainedby appropriate use of selected shims 112. Preferably there are twocircular scrapers (see FIGS. 10 and 13) 114 and 116 for each scraper 38or 40 previously generally described. The circular scrapers 114 and 116have splits 117 (FIG. 11) and are spring loaded so that the said rings114 and 116 resiliently engage and scrape tubular members 34 and 36. Agroove 119 is provided in each ring 114 and 116 and with such groove inregistration with the longitudinally alined openings 118 (in tubularmembers 34 and 36). If the rings 114 and 116 are to be operated when thesaid openings 118 are not being used to spread adhesive, then suchgrooves 119 may be eliminated. However, if said rings 114 and 116 areused for scraping during normal operation of openings 118, then suchgrooves 119 provide for lateral air adjacent an opening 118 which tendsto prevent build-up of adhesive adjacent the opening 118 over which aring 114, 116 is registering. Preferably the rings 114 and 116 have awidth, as respects the spacing of openings 118, so that only one opening118 is covered. By such lateral air and the width of rings 114 and 116,no substantial interference of the free flow of air from openings 118results. Any substantial interference with air leaving said tubularmembers 34 and 36 through openings 118 would cause malfunctions inuniform adhesive spread and thus must be prevented. In order to provideprecision in the alinement of the grooves 119 in the circular scrapers114, 116 and the alined openings 118 in tubular members 34 and 36, pins120 are provided which fit into openings jointly provided in housingparts 108 and scrapers 114, 116 of scraper members 38 and 40. Therelative angular position of the scraper housing parts 106, 108 isdetermined by plates 122 locking the relative angular position betweenthe housing parts 106, 108 and the cross frames 79.

The individual veneer guides 82 are secured to the cross frames 79 byset screws 124. In order to positively determine that each of the veneerguides 82 and 84 will project identical distances away from cross frame79, selected shims 126 may be suitably employed.

Scraper members 38 and 40 may be secured to the endless cable means 42by any suitable means, such as clevises 128, best shown in FIGS. 2, 7,10, 14, and 15.

The internal structure of each scraper 38, 40 is illustrated in asomewhat enlarged view in FIG. 13. The scraper housing parts 106, 108are provided with similar inclined tracks. In FIG. 13, the housing part108 has two inclined spaced apart track portions 130 and each scraper114, 116 has mating, inclined surfaces with said track portions 130.Thus, as the housing part 108 is moved toward the right (as respects theshowing in FIG. 13), the scraper blade 116 is urged downwardly and intoclose scraping contact with a tubular member 36. Also, it will beapparent upon movement in the other direction, that the circular scraper114 will be moved into close scraping contact with a tubular member 36.Thus, as the scrapers 38 and 40 are caused to travel first in onedirection relative to the tubular members 34, 36 and then in the otherdirection, that the said tubular scraper members 38 and 40 will cleanlyscrape foreign materials which may accumulate on the external peripheryof the tubular members 34 and 36. Preferably the rings of the scrapers38, 40 will not scrape over the alined openings 118 in the said tubularmembers 34 and 38. Also, the scrapers 38, 40 may be operatedperiodically or continuously, as desired.

In addition to providing close contact between scrapers 38, 40 and thetubular members 34, 36, it is preferable to provide at the time ofscraping contact, a diluentor solvent-cleaning liquid for the residue,including the adhesive used, to aid in cleaning the said scrapers andthe said tubular members. One construction for such purpose is bestshown in FIGS. 15 and 16 of the drawings. The

scraper 38 for the tubular member 34 is provided with passageway 132 sothat liquids entering the same communicate with the circular scraper114, 116. A container 134 for said cleaning liquid 136 is provided withinlet valve means 138 so there is a supply of cleaning liquid 136 underpressure. Spring loaded, outlet liquid valve means 140 is positioned inthe path of travel of tubular scraper member 38 so that at the end ofthe travel of the tubular scraper member 38 in one direction and towardthe container 134, the movement of the scraper member 38 upon contactwith said valve means 140 will actuate the said valve means 140 and apredetermined amount of cleaning liquid 136 will be injected upon thecircular scrapers 114, 116 of the upper tubular scraper member 38. Thelower tubular scraper member 40 is similarly equipped and during itstavel when it contacts the valve means 142 (similar in function to thevalve means 140), a predetermined amount of cleaning liquid 136 Will be.injected upon the circular scrapers 114, 116 of the lower tubularscraper member 40. In this form of the invention, cleaning fluid 136 isinjected periodically upon the circular scrapers 11.4, 116 of thescraper members 38, 40 when said scraper members consecutively contactthe outlet.- valve means 140 and 142.

The modified form of structure to provide cleaning fluid to the saidcircular scrapers 114, 116 of tubular scrapers 38, 40 is shown in FIG.17 of the drawings. As an illustration, the tubular scraper 38 isprovided with passageways 144 communicating between circular scrapers114, 116 and inlet passageway 146, which in turn connects to a flexibleconduit 148 connected to a suitable source (not shown) of cleaning fluidunder pressure which will be similar, in that respect, to container 134and cleaning fluid 136 therein. In this form of the invention, cleaningfluid will be discharged (whenever pressure is applied to the liquid inconduit 148) on the circular scrapers 114, 11.6 of each of the tubularscrapers 38, 40 and at intervals regulated by any suitable valves means(not shown). A similar construction to that shown in connection withtubular scraper 38 of FIG. 17 will be used in connection with thetubular scraper 40 and thus both constructions are now obvious.

The structure employing veneer guides 82, 84 will be operated inconjunction with the veneer 26, which veneer travels in a directionlengthwise of the wood grain thereof. Thus, the axes of the usual ridgesand valleys present in dried veneer to which adhesive is to be appliedto one or both surfaces, will be parallel to the direction of travel ofthe wood veneer 26. If said veneer 26 is utilized as cross banding stockof plywood, it will have adhesive spread on its upper and lowersurfaces. If such veneer is used elsewhere in the manufacture ofplywood, only one surface, as the upper surface, will have adhesivespread thereon. In such instances, only an upper adhesive applicatorroll 20 will be employed and a lower adhesive applicator roll 28 willnot be employed. Because of the surfaces to be coated with adhesive, thefact that the veneer 26 is traveling in the direction of its Wood grain,the veneer guides 82 and 84 will be adequate to keep the veneersufficiently flat and properly located at the time the veneer 26 passesbetween tubular members 34 and 36 or merely below tubular member 34.

However, if the veneer sheet is traveling in a direction crosswise ofits wood grain (as depicted by veneer sheets 150 in FIGS. 8 and 9) thenmodified veneer guides are used for veneer guides 82 and 84 and themodified adhesive applicator rolls are used for the upper and loweradhesive applicator rolls 20 and 28. In order to simplify the drawings,FIGS. 8 and 9 show generally only the modification and the remainingparts generally not shown and 154 are elongated in length to iron outridges and valleys in the dried veneer which ridges and valleys aretraveling crosswise of the machine due to the direction of travel of theveneer crosswise of its wood grain. The upper and lower adhesiveapplicator rolls 156, 158 replace the upper and lower adhesiveapplicator rolls 20, 28 of the other figures. Also, the upper and loweradhesive applicator rolls are provided with grooves 160, 162 to permitvertical movement of the elongated veneer guides 152, 154. Thestructures of FIGS. 8 and 9 is of particular utility in applyingadhesive to one or both surfaces (upper and lower) of veneer which issubstantiall a continuous sheet. When cross-banding stock has compriseda plurality of pieces of veneer edge joined together to form acontinuous sheet, the problem of applying a uniform spread of adhesivehas proved to be insurmountable in prior art devicesthe adverse resultsin spreading adhesive crosswise of the grain has been much more than inthe other direction. However, such continuous sheet of cross-bandingstock can be readily caused to travel crosswise of the direction of itsgrain through devices of this invention and at the same time with auniform spread of adhesive.

The forward end portions of the veneer guides 152, 154 and the tubularmembers 34 and 36 are supported in the same fashion as that indicated inthe previous figures through cross frames 79 and thus the sameadjustments obtain for the veneer guides 152, 154 as obtained for theveneer guides 82, 84.

In the foregoing, references have been made to the applying of anadhesive coat to wood pieces of veneer 26 or veneer sheet (formed of aplurality of edge joined wood veneer pieces). These are to be consideredas examples of a core to be faced with other pieces of wood veneer oneither the top or bottom thereof, or both. Other cores will includeproducts commonly termed in the art as chipboard, hardboard, flakeboard,and lumber stock. To such cores, a wood veneer front or back face (orboth) is to be consolidated by a glue line. The adhesive to be appliedto provide such glue line may be applied to the core with a double glueline or it may be applied to the inner surface of the wood veneer facingby a single glue line.

The adhesive employed may be either a hot press type or a cold presstype. With either type, pressing is necessary to provide the necessaryintimate contact between the surfaces to be adhered together. If theglue line is not uniform in thickness, then inadequate glue lineresults. With hot pressing, nonuniform thickness of glue line oftenresults in blows, blisters, areas of noncured adhesives, and sparse(thin or starved) glue line areas. With cold pressing, nonuniformthickness of glue line often results in too thick or too thin glue linesand inherent adverse results. The conventional glue spreader rolls 20and 28 provide a common thickness but of two items, (1) of core, asveneer 26, and (2) of adhesive, as the top and bottom layers ofadhesive. Wood veneer stock to be veneered to a core is commonly rotarycut or sliced. With sliced wood veneer stock, we have a surface which ischaracterized by having a nonplanar surface with ridge and valleydeviations from a planar surface. Such deviations are multiplied andexaggerated with the rotary cut veneer because of inherent conditionspresent during rotary cutting. Regardless of the type of wood veneerused or the type of wood core stock employed, the said conventional gluespreader rolls 20 and 28 tend to provide thicker glue lines in thevalley deviations and thin or sparse or starved glue lines in the ridgedeviations. Also, as the liquid adhesive is noncompressible, theadhesive in said valley deviations tends to maintain separation of thewood surfaces during pressing resulting in the adverse resultspreviously mentioned either in cold or hot pressing.

With this invention, the doctor rolls 22 and 30 are adjusted relative tothe upper and lower adhesive rolls 20 and 28 to provide for an overspread or excess spread of adhesive over that determined as the ultimatefor the type of pressing used and the particular grade of wood employed.Thus, by way of example, if it is determined that the final glue spreadshall be at the rate of about 60 pounds of wet glue line per thousandsquare feet of double glue line, then said doctor rolls 22 and 30 willbe adjusted to spread at the rate of about 70 pounds of wet glue lineper one thousand square feet of double glue line.

Air under pressure is provided in the tubular members 34 and 36 and inthe range of to 50 p.s.i. The openings 118 in said tubular members havea diameter preferably in the range of 0.024 to 0.062 inch and they arepreferably spaced apart different distances in the range of 0.10 to 0.25inch. Referring to FIGS. 11 and 12, the walls providing the openings 118are maintained so that the downwardly directed jet of air from the uppertubular member 34 and the upwardly directed jet of air from the lowertubular member 36 impinge at an acute angle to the traveling wood stock,as veneer 26. Such acute angle is preferably in the range of 6080.

Such jets of air distribute adhesive to a controlled adhesive thicknesson a wood surface even though the said wood surface has the usualnonplanar surface with ridge and valley deviations from a planar surfaceand even though the wood stock is of nonuniform thickness. Where we havevalley deviations, obviously, there will be greater deposits ofadhesives in said valleys. Also, where we have variations in thicknessof the wood stock, the thicker the wood stock, the thinner the adhesivecoating and the thinner the Wood stock, the thicker the adhesive coatingto a point. Obviously, if the thickness of the adhesive on one of theadhesive rolls or 28 is not sufficient to contact the surface of thewood stock, then there will be no deposit of adhesive in view of theextra thinness of the wood stock.

In the prior art, it was the tendency to increase the rate of adhesivespread whenever pieces of Wood stock had observable area on which noadhesive was present. While such practice of increasing adhesive spreadto cure the problem of barren areas on which no adhesive appeared, suchpractice created more difficult ones and particularly those involved inexcessive adhesive spread. In view of the fact that the presentinvention contemplates the applying initially of excessive adhesive,then the prior art problems resulting from initial overspread ofadhesive are no longer present as the tubular members 34 and 36 willremove all excess of adhesive over a final predetermined adhesivethickness spread. All excess adhesive will be moved by the air streamemitting from the openings 118 toward adhesive rolls 20 and 28 and suchexcess will be picked up by such adhesive rolls.

Previously, curtain coating, spraying, and dipping have been attemptedto apply adhesive to the surfaces of wood stock to be adhered together.Such practices of the prior art have had the shortcoming of nonuniformadhesive spread, including areas of excessive adhesive spread, and theiruse in the practical arts has been rather insignificant as compared tothe use of adhesive applicator rolls, such as 20 and 28. However, suchcurtain coatings, spraying, and dipping to provide an initial coat orlayer of adhesive on wood stock can well be used in combination with thetubular members 34 and 36 as it is desired to initially provide anexcess coating or layer of adhesive.

The tubular members 34 and 36 are provided with a plurality of spacedand longitudinally alined openings 118 and thus the surface of theadhesive finally remaining is characterized by laterally spaced apartslight valleys and ridges extending in the direction of travel of theWood stock. Such valleys and ridges of adhesive are not of sufficientmagnitude to cause any substantial variation in the uniform thickness ofthe final adhesive spread. Rather than harming, such valleys and ridgesaid in the final adhesion of the wood surfaces to be contacted andadhered together by an adhesive. With slight variation and the presenceof slight excess of adhesive in the ridges in the final adhesivethickness and where the adhesive is provided to a substantially uniformthickness, then migration of adhesive brought about during the pressingcycle causes more intimate contact between the wood surfaces and theadhesive resulting in better glue lines. One theory as to why suchslight variations from absolute uniformity of adhesive thickness ishighly desirable and useful, resides in the fact that the adhesive isapplied directly to only one of the wood surfaces to be adhered togetherand if slight migration occurs during pressing, this relative movementcrosswise between the wood surface and the adhesive enhances thespreading of the adhesive on the wood surface on which no adhesive wasoriginally deposited. Such limited migration is to be distinguished fromthe relatively large migration which occurred in the prior artpractices. If pools or wells of adhesive are left, they will not move tothe desired extent by migration and will remain pools of adhesive whichbecome incompressible separators between the wood surfaces, preventingwood contact and proper bonding.

Regardless of the theory, this invention provides for uniform andpractical results by utilizing the spaced apart longitudinally alinedopenings 118 rather than a continuous slot. Attempts have been made toutilize a continuous slot but without success. The thickness of theadhesive coating required on wood varies with the grade quality of thewood, the specie of the wood stock, and characteristics of the adhesive.Thus, the adhesive spread required may vary from 50 pounds to pounds perdouble wet glue line per 1000 square feet of wood surface. By the use oflongitudinally alined spaced apart openings 118, then variations in theair pressure to tubular members 34 and 36 result in variation in thethickness of adhesive spread and the results from varying said airpressure on the thickness of the final glue spread are readilypredictable and controllable. On the other hand, with a continuous slot,such predictable and controllable results are absent.

In the event that the initial coating of adhesive is provided byadhesive applicator rolls, such as 20 or 28, and the amount of excessadhesive is determined by the adjustment of doctor rolls 22 and 30, thenall excess of adhesive over a predetermined uniform thickness ofadhesive applicator rolls 20 and 28.

Veneer 26 may be formed from one or more than one piece of wood veneer.When formed from more than one piece, the said pieces are preferablyedge joined together so that they are handled as one piece. However, theveneer depicted as veneer 26 will be traveling in a direction parallelto the wood grain. Such a piece of veneer 26 will have a surface portionhaving many deviations from a planar surface and such deviations resultfrom the mechanical means slicing or in rotary cutting the veneer,difference in the wood stock or trees providing the veneer, anddifferences resulting from uneven drying of the veneer after the samehas been cut. These deviations of the surface of veneer 26 from a planarsurface include not only ridge and valley deviations but also inthickness variations. The thickness variations are found in a singlepiece of veneer and between pieces of veneer which may form the veneerpiece 26. Also, the adhesive applicator and veneer conveyor rolls 20 and28 wear and change in diameter as well as in surface contour andtherefore do not accurately spread the adhesive on a veneer sheet toeven a composite uniform thickness of veneer sheet and adhesive. Thus,the present invention in providing a common thickness of adhesive onveneer stock 26, traveling in the direction of the wood grain, hasprovided a very substantial contribution to the prior art and has solveda long felt need.

The problem of providing an even thickness coating of adhesive on thesurfaces of the edge-joined-together pieces of veneer stock, travelingin a direction crosswise of the wood grain, is an even more complexproblem. Referring to FIGS. 8 and 9 of the drawings, the veneer sheet150 is formed of a plurality of pieces of veneer which have been edgejoined together to form a continuous sheet of veneer. The surface of thesaid sheet 150 has deviations from a planar surface by difference inthickness in different areas of a single piece of veneer, differentthicknesses of pieces of veneer forming the sheet 150, deviations byridges and valleys from a planar surface, and has rather long undulatingridges and valleys extending crosswise of the direction of travel of theveneer due to the fact that the sheet in drying tends to form suchcontour because of differences of shrinkage in various areas obtainingduring the drying process of the veneer. Different densities of the woodin different areas forming a sheet, both rotary cut and sliced veneersheets, tend to enhance the formation of long undulating ridges andvalleys and the veneer sheet .150 does not tend to lie flat and does nottend to assume a definite position.

Thus, in FIGS. 8 and 9 of the drawing, the upper and lower veneer guides152 and 154 are somewhat elongated to iron out the long undulatingridges and valleys which are caused during the drying process of theveneer. It is desirable that wood stock or veneer be held flat and in apredetermined position at the time of impingement of the air throughopenings 118 so that the angle at which the said air is impinged on thesheets of veneer 26 or 150 and the relative position of tubular members34 and 36 to the wood stock can be controlled within the limits of thisinvention.

The prior art has suggested continuous processes of laying up plywoodand all of such processes, which have been given serious considerationin the art, have contemplated the use of a continuous sheet of core laidup by edge joining pieces of veneer to form a continuous sheet, such asveneer sheet 150. The most serious difficulties encountered inattempting to apply said proposed continuous lay up of veneer has beenthe providing of an even spread of glue on both faces of travelingveneer stock traveling in a direction crosswise of the wood grain of thestock. However, with the present invention, the problem of providing auniform thickness of adhesive to the surface of the traveling wood stockhas been demonstrated to be successful even though the surfaces of saidtraveling wood stock have deviations from a planar surface as indicated.Thus, the present invention makes many of the prior art contemplatedprocesses of continuously laying up plywood now practically feasible.

In order to positively control the amount of glue remaining on a woodsurface, such as veneer 26, the openings 118 are disposed in closeproximity to the adhesive on the surfaces of said veneer 26. Thus, someof the adhesive will become air borne and will be carried onto thetubular members 34 and 3-6 and such tubular members 34 and 36 must beperiodically cleaned. This is accomplished by the scraper members 38 and40. If operations would permit the cleaning of the tubular members 34and 36 While air is not being delivered out openings 120, then thecircular scrapers 114 and 116 of the scraper members 38 and 40 may becontinuous circular scrapers. However, it is generally desirable toprovide for a continuous availability of the spreading of adhesive andhence, normally, the circular scrapers 114 and 116 must function toclean the tubular members 34 and 36 While air is being ejected throughopenings 118. Thus, preferably, there is provided the grooves 119 in therings 114 and 116 and the rings 114 and 116 are of a crosswise dimensionof less than a spacing between openings 118. Thus, a circular ringscraper 114 or 116 will be in registration with only one opening 118 atany particular time period and at that time, air from that particularopening 118 is permitted to exhaust in a lateral direction and which airtraveling laterally tends to clean the space in tubular members 34 and36 adjacent the particular opening 118 involved.

In cleaning the outer surfaces of the tubular members 34 and 36, weencounter deposits of adhesive and also deposits of adhesive mixed withforeign matter. Thus, the material to be scraped and to be moved tendsto adhere to the said tubular members. Thus, preferably, a cleaningliquid, of the adhesive solvent or adhesive diluent type, is preferablyemployed. Thus, there is illustrated the cleaning liquid 136 of FIG. 16,or a similar liquid which is delivered to the flexible conduit 148 ofFIG. 17, which is delivered to the circular scrapers 114 and 116. Thesaid circular scrapers 114 and 116 are spring loaded to resiliently urgethemselves around and adjacent the tubular members 34 and 36 and thusaugment their clening-scraping action. The said scrapers 114 and 116 aresplit rings with splits 117 and thus may be provided with the resiliencyand tendency to follow the surfaces of the said tubular members 34 and36. If desired, additional pressure is obtained urging said circularscrapers 114 and 116 against the tubular members 34 and 36 by reason ofthe inclined surfaces or inclined tracks 130 shown in FIG. 13 of thedrawings cooperating with said scrapers 114 and 116.

I claim:

1. Apparatus for providing controlled adhesive spread on traveling woodsheet stock, said stock being characterized by having a nonplanarsurface with ridge and valley deviations from a planar surface and byhaving a nonuniform thickness, comprising wood sheet stock conveyormeans; adhesive applying means providing an adhesive coating on saidstock; an adhesive moving air knife comprising a tubular member, the airoutlet of which comprises a plurality of spaced longitudinally alinedopenings, said air knife providing an air stream disposed at an acuteangle to the surface of said adhesive on said stock, directed counter tothe travel of said stock, removing adhesive from adhesive over a pre- 0determined thickness present by reason of ridge and valley deviationsfrom a planar surface of stock and by 'thinness of said stock, andadding adhesive to adhesive under a predetermined thickness present byreason of ridge and valley deviations from a planar surface of stock andby thickness of said stock; and tubular scraper members mounted forreciprocating travel on said tubular member and in scraping-cleaningposition relative to the external surface thereof.

2. The combination of claim 1, wherein said scraper means are providedwith a groove disposing in noncontacting relation with said tubularmember and which groove registers with the spaced apart longitudinallyalined openings in the tubular member avoiding scraping the area inwhich said openings are located and which groove functions to deflectair in said longitudinal direction.

3. The combination of claim 1, wherein a solventdiluent cleaning liquiddispenser delivers cleaning liquid to said tubular scraper means.

4. The combination of claim 3, wherein said cleaning liquid dispenserintermittently delivers cleaning fluid to said tubular scraping means.

References Cited UNITED STATES PATENTS ALFRED L. LEAVI'IT, PrimaryExaminer C. R. WILSON, Assistant Examiner US. Cl. X.R.

